When joint replacements were introduced in the orthopeadic treatment and surgery of the locomotor system, physicians were confronted with technical and surgical problems which they had not been prepared for at medical school.
Surgical processes forming the basis of such new technologies in medicine can only be practiced successfully if the risks, incorrect planning and errors during surgery and in pre-operative and follow-up treatment are taught, presented and substantiated.
Histological material was obtained during operations to replace prostheses. A critical evaluation of artificial hip joint implants with poor results showed that the main reason for prosthesis loosening was the incorrect implantation of the prosthesis' components.
Moreover, macroscopic and microscopic, histological findings in joint implants--some of which had been in place for over 20 years and had been taken from deceased patients--showed that the cementing techniques and their results often differed greatly and were often the major reason for poor results.
Errors made when inserting a prosthesis can be due, for example, to the poor or incorrect preparation of the prosthesis' bone bed. The goal of improved implantation techniques is very similar to that of dental implants: to provide an implant bed which is as clean and dry as possible.
Examining the end of the medullary canal, bone cement penetration, anchoring in the proximal femur, the position of the prosthetic components, avoiding the creation of gaps while the bone cements are hardening and removing excess cement while and after the cement components harden are only a few of the criteria the surgeon must master and be able to evaluate.
Evaluating and making use of the pressure build-up in the cement applicator during the application and hardening of the bone cements are of utmost importance in improving cementing techniques.
The modern methods used in the treatment of fractures and in joint replacement are taught in courses in surgery. It is primarily practicing surgeons in orthopeadics and traumatology who are invited to these courses. These courses teach, above all, preparing the bony support, anchoring techniques for the prosthetic components and the position of the prosthetic components in the bone; they also deal with potential errors made in these procedures.
Evaluating the results of surgery in such courses encounters a particular obstacle, however: Implants inserted in bone can only be judged with precision if the bone and the implant are both cut open together. Most prosthetic components are made of a highly resistant material such as metal, ceramic or high-strength plastic. As a result, this is impossible due to the highly complicated separation process.
In research and in the laboratory, it is not possible, for economic and procedural reasons, to perform relatively large series of implantations with known prostheses in order to perform systematic research on the surgical techniques and potential errors.